Method of making piston rings



' v. F. ZAHODIAKIN METHQD OF MAKING PISTON RINGS Filed April 10, 1934 3 Sheets-Sheet 1 Wm I INV'ENTOR W MM ATTORN EYs March 28,1939.

V F. ZAHODIAKIN METHOD OF MAKING PISTON RINGS Filed April 10, 1954 5 Sheets-Sheet 2 ATTO RNEY March 28, 1939. v. F. ZAHODIAKIN METHOD OF MAKING PISTON RINGS Filed April 10, 1954 3 Sheets-Sheet 3 R o T N E v m ATTORNEYS Patented Mar. 28, 1939 PATENT I OFFICE 2,152,127 METHOD or MAKING PISTON runes Victor F. Zahodiakin, Cincinnati, Ohio, assignor to The Z-Flex Piston Ring Corporation, a corporation of New Jersey Application April 10, 1934, Serial No. 719,885

14 Claims.

This invention relates to piston rings, and is particularly directed to a method of making the same. This applicant's co-pending case Serial Number 696,470, filed October 30, 1933, discloses and claims one form of improved piston ring which can be fabricated by means of the present method.

These rings are formed from a strip of flexible sheet material. The strip of metal is formed to provide a circumferentially extensible and compressible ring, which is highly sensitive and dilates to local as well as general irregularities in the cylinder wall. The strip of metal is bent or swaged to provide a series of passageways which open at. the inner and outer peripheries of the ring. For this purpose the strip is bent to form corrugations or reversely bent portions.

Each ring, as supplied to the trade, has the throats of its corrugations narrowed down but without the opposing edges in contact. When the ring is placed in the cylinder, the opposing edges substantially abut so that the passageways have substantially closed side walls. Clearances afforded at the throats of the corrugations permit installation and subsequent dilation of the ring when in use and as wear occurs.

It is desirable that the top and bottom surfaces of the ring as installed be perfectly fiat or continuous without depression, since full sealing contact with the horizontal walls of the ring groove is then provided. Therefore, to accomplish these top and bottom surfaces without undulation, it is essential that the bends of the corrugations be relatively sharp so that when the adjacent cross edges at the throat of each corrugation are brought together there are no depressions such as would occur if these edges were rounded.

Therefore, it is the general object of this invention to provide a method of forming a piston ring by corrugating a strip of fiat flexible sheet material. It is preferable to feed the strip in a continuous straight length and to curve the strip laterally to the proper or finished radius.

It is the more specific object of this invention to provide a method of fabricating a ring as aforesaid, which ring is corrugated, or the material of which is reversely bent upon itself to form oil passageways with the bends forming the corrugations made square so that flush and substantially continuous top and bottom surfaces are provided for the ring without undulation.

It is a further object of this invention to provide a method of fabricating a ring as aforesaid, which method corrugates the material or reversely bends the same upon itself with the throats of the corrugations substantially closed, each corrugation providing abutting throat suraces.

Other objects and further advantages will be 5 more fully apparent from a description of the. accompanying drawings, in which:

Figure 1 is a diagrammatic view, illustrating the first stage in the method of forming the strip of material from which the ring is cut, in 10 which view the indexing mechanism has just fed the strip and the first dies of the rough corrugation forming unit are in action.

Figure 2 indicates the second stage, wherein the forming dies are re-engaging the last rough 15 corrugation which has been formed, the finishing dies for the corrugations are set for the swaging stroke for providing relatively sharp corners for the corrugations, and the corrugation closing dies are about to act.

Figure 3 is a view illustrating the third stage of construction, wherein the corrugation formed in each cycle of operation is being formed, the finishing or swaging dies have completed their strokes, and the corrugation closing dies have 5 been operated.

Figure 4 is a diagrammatic view, illustrating all dies in position at the end of a cycle.-

Figure 5 shows all dies in retreat position and the strip being advanced one corrugation.

Figure 6 is a top plan view of the strip, illustrating the curved form which it takes during its formation.

Figure 7 is a fragmentary detailed view, illustrating modified dies for closing the corruga- 35 tions.

Figure 8 is a perspective view of the finished ring.

In the side views of the strip in the process of formation, the curved nature of the strip, as 40 shown in plan view, is disregarded for the sake of clearness. In the plan view the initial curvature of the ring is shown greater than the normal curvature for the purpose of spreading out the mechanism. The straight-strip material, from 5 which it is preferable to form the rings, may be supplied from a roll to the machine for performance of the method herein set forth. The operating mechanisms for the dies are not disclosed since the present invention deals solely 50 with the forming of the metal. The following units in the order mentioned act on the strip to produce the ring:

First, a group of dies ill bend the metal into rough corrugated or zigzag form. Second, a set 55 of 'sw'aging dies ll act on the corrugations at one side of the ring for squaring the corners and providing the relatively sharp cross edges previously mentioned. Third, a set of swaging dies 2, duplicating the second set, acts on the ring from the other side for the purpose of squaring the remaining corners of the corrugations. Fourth, a corrugation closing mechanism I3 acts to partially close the throats of the corrugations. A cut-off mechanism M is provided as well as indexing fingers l5 for a gauged feed or step up of the strip, one corrugation at a time.

By the method chosen for the purpose of illustration, the piston rings are formed from a continuous length of straight strip stock. Therefore, it is a part of the operation accomplished during the formation of the corrugations, or resulting oil passageways. in the finished ring, that the dies act to curve the strip of metal laterally. The forming dies of the group which act on the metal initially to bend or form up the rough corrugations are arranged generally in an arc for the purpose of causing the curvature above mentioned.

The initial arc of formation is prescribed on a greater radius than the radius of the finished ring. The cross walls of each forming die of this curve are disposed in planes radial to the center of the finished ring. Accordingly, it will be observed that a differential is imposed to the edge lengths as the first phase in the formation of the 1% the final operations on the corrugations, wherein the corrugations are closed, the radially disposed cross walls of the corrugations are brought closer together and the radius of the arc is shortened so that the radial cross edges, which lie in the top and bottom planes of the ring, when brought toward each other will abut. The corrugations are closed by means of elements radially disposed relative to the center of the ring and moving on the ring center, and the arc of curvature is changed to the true curvature of the ring.

The corrugations as originally formed are of considerably greater depth than the normal height or axial dimension of the finished piston ring. The swaging actions for squaring the corners decrease the height in each instance and the operation of drawing the corrugations together for closing the throats thereof further decreases the height.

The first set of forming dies is adapted to form two corrugations when the operation is first started. Thereafter since the strip is fed a distance of one corrugation at each indexing movement, the most advanced corrugation of the pair is again engaged by the mechanism and from then on a single corrugation is formed in an operation.

Accordingly, ignoring the formed corrugations in Figure l, forming dies I6, engage or grip the strip from opposite sides. One of these dies, namely I6, is plain whereas the other, namely l1, includes a shoulder l8.

A third die l9 engages the strips on the side opposite to the shouldered die for the first bending operation in the cycle being described. This third die is also shouldered, one shoulder, namely 2|, and the one adjacent the plain die, is offset the thickness of the material, and the other, namely 22, is offset the width of a corrugation including its walls. Accordingly when the third die is brought into full play, a double bend has been formed as shown in Figure 2, that is to say, the metal has been turned to form a cross wall 23 aware? and a longitudinal wall 24 out of the plane of the strip.

A fourth die, namely 25, is then brought against the strip on the side opposite to the third die, this die being a duplicate of the third die and operating alongside of the upper shouldered die. A double bend is again formed and a corrugation has been completed.

The fifth die, namely 26, a duplicate of the third and fourth dies, then approaches the work from the opposite side to the fourth die and repeats the process of forming one side of a cormgation. The sixth die, namely 21, operating on the same side as the fourth die, does not include the wide shoulder since there is no cooperation with this die for the purpose of forming further corrugations. It will be seen from Figure 4 that two complete corrugations have been formed.

At this time the dies are separated and the strip is fed one corrugation by means of index fingers I5 (see Figure 5). In the next cycle of operation of the mechanism just described, the last corrugation formed is simply reformed, that is to say, the dies l6, l1, l9 and 25 of the mechanism In operate over a formed corrugation. These dies all include rounded edges and the result is that the corrugations are roughly formed with rounded cross edges.

The next mechanism or movement includes swaging dies and is of the following nature. An anvil element 28 approaches the strip from above. This element includes an extension 29 adapted to extend into the corrugation and shoulders 30, 30, at each side and adapted to engage the tops or horizontal walls of the adjacent corrugations. Plain anvil elements 3|, 3|, operating together in spaced relation at the opposite side of the strip, engage into the corrugations at each side of the one entered by the above-mentioned anvil. It

will be noted that the projected portion of the anvil does not extend entirely to the bottom of the corrugation in which it is engaged and has rounded cross corners. The operating die 32 acting on the metal within the mold passes between the plain mold elements and has sharp cross corners 33, 33. Thus when this latter element engages the horizontal wall of the corrugation it presses the metal, displacing the mass to provide sharp outer cross corners and fillets on the inner sides of the corrugations. It will be seen that there is an excess of metal for this purpose over and above that required to fill the space when the dies are brought together on the swaged wall.

The third mechanism is a duplicate of that just described. However, it acts on the opposite side of the strip and operates on those corrugations which open to the opposite side of the strips. In other words, the second and third mechanisms operate on the opposite horizontal walls of the ring.

The fourth mechanism acts on the corrugation for closing the throats thereof. The parts of this mechanism are radially disposed relative to the finished ring center and enter the corrugations laterally. An anvil 34 successively enters the alternate corrugations. This element is slotted so as to provide a support 35 above the cross wall of the particular corrugation and a support 34 of triangular cross section for the corrugation side walls while these walls are being bent or inclined for closing the throat of the particular corrugation. At the opposite side of the strip a support 36 is provided which includes a vertically operating separator plate 31. This plate passes into the throat of the corrugation as shown in Figure 3.

Laterally and longitudinally moving. forming elements 38 engage within the corrugations at each side of the one being held or operated on. These fingers are brought together longitudinally, engaging the cross edges 39, 39, of the throat against the separator plate. This plate acts as a gauge for providing uniform gaps in the throats of the corrugations. When the corrugation has thus been closed, the fingers are disengaged laterally and the strip is then fed to bring up the next corrugation. The support 35 prevents displacement of the horizontal wall, as the side walls are bent into position.

In Figure 7 the support portion t l of the or side walls of the corrugations are parallel at the throats thereof as at 40, providing right angle cross edges. This is advantageous as opposed to cross edges havingacute angles resulting from entirely inclined walls. If wear takes place on the horizontal wall in a construction having the side walls receding the gaps will be unduly. increased. In the form under discussion the gaps remain the same despite wear.

The cut-off mechanism l4 includes upperand lower knives 4|, 4|. These knives cooperate to make a dovetail cut 42. Since the cutends' of the finished circular section are complemental, these ends are readily interfltted or hooked together and welded for completing the circular structure shown in Figure 8.

The rings produced in the foregoing methjod may be machined to accurate dimension; For this purpose the top, bottom and outer periphery. may be ground. 1 I

Having described my invention, Iclaim:

1. The process of forming a piston firing of flexible strip material, consisting'of bending said I strip into zigzag shape, successively die-pressing, the corrugations to obtain squared corners and i thereafter substantially closing the throat of each corrugation whereby cross passagew ys are,

formed opening at the inner and outer peripheries tially closing the throats of the corrugations.

3. The process of forming a piston ring of a strip of flexible sheet material, consisting of bend-- ing the metal to provide corrugations, and draw-- ing the throat portions of the cross walls thus formed together for substantially closing the open sides of the corrugations and providing cross passageways.

4. The process of forming a piston ring from a strip of thin flexible shet material consisting of bending the metal to form corrugations, forming each corrugation to provide sharp cross edges, forming the side Walls of the corrugations for substantially closing the throats of the corrugations, and in the formation of said side walls providing substantially abutting flat surfaces.

5. The process of forming a piston ring of a strip of flexible sheet material consisting of bending the metal to provide corrugations, drawing the portions of the side walls of the corrugations icest radial' fl met when .the I circumference-j 1 toward the open ends thereof together, and controlling the drawing movement for preventing complete closing of the throats of the corrugations.

6. The process of forming a piston ring of flexible strip material consisting of bending said strip to form rough corrugations, and thereafter internally and externally supporting each corrugation and swaging the outer wall of the corrugation to form square corners therefor.

'7. The process of forming a piston ring from strip-material, consisting of corrugating said material, internally supporting a portion of the side walls and the end wall of each corrugation, drawing the outer ends of the walls together for closing the throats of the corrugations, and in this operation forming adjacent flat throat surfaces, the portions of the walls between the support means and the drawing means being inclined.

8. In the process of forming a piston ring from a straight flat strip of flexible material, the step of bending corrugations in the material providing cross edges disposed radially from a common centerand curving the strip simultaneously with the formation of the corrugations.

9. The process of forming a piston ring from a straight'flat strip. of flexible metal, consisting of corrugating the met'alproviding cross edges disposed radially relative to a common center, substantially closingthe throats of said corru gations,. and curving the strip laterally during said process.

10. The processfor forming a piston ring from a 'flat strip of flexible material, consisting of corrugating the strip and thereafter drawing flat throat portions of the corrugations together leavingthe inner portions of the corrugations as originally formed to provide cross passageways opening at the inner and outer peripheries of the ring. r

11. The processof: forming a piston ring from a; strip of flatflexible material, consisting of corrugating. the .1 stripand: thereafter "drawing;

' 'alls'ofl the corruga-j I flat'adja-' alls. dapted to make flush abut- 12. The process of formingjafpistonring from flexible strip materialv consistingof bending said strip to form corrugations,andithereafter drawing'adjacent portions of the Walls of. the corrugations at the throats thereof togetheribyfmeans of tools moving circumferentially of the ring and I laterally against the vertical walls' bf the'corrugations, whereby. each corrugation provides a passageway opening at theinnerfiahd outer periphery of the ring. j

13. The method-of forminga piston ring from a strip of metal, consistinggofbending the stripto form corrugations andw'thenclosing the cor- I rugations, said closing operation forming the corrugations into substantially closed tubes functioning as cross passageways.

14. The method of forming a pist 11 ring from a strip of metal comprising the steps of, forming a corrugation in the strip, supporting the side Walls of the corrugation against displacement, and engaging the crownwall of the corrugation between dies, the side edges of which dies lie on radial lines. and the outer'of which dies includes sharp corners for the purpose of swaging the crown wallsand forming sharp crowns thereon.

VICTOR F. ZAHODIAKIN. 

